Carbohydrate Chemistry - Biochemistry PDF

BIOCHEMISTRY carbohydrates Bio-Philic Dr. Ibrahim El-Husseiny Carbohydrate chemistry They are the most abundant form of organic matters on the earth ‫عل سطح االرض‬ ‫ه اشهر المركبات العضوية...

BIOCHEMISTRY carbohydrates Bio-Philic Dr. Ibrahim El-Husseiny Carbohydrate chemistry They are the most abundant form of organic matters on the earth ‫عل سطح االرض‬ ‫ه اشهر المركبات العضوية الموجودة ي‬ ‫الكربوهيدرات ي‬ They are poly hydroxy aldehyde or poly hydroxy ketone or their derivatives )‫(مشتقاتهم‬ Carbohydrates Contain the elements )‫(عنارص‬: C, H, O Produced by fundmental pathway )‫ ;(طريقة اساسية‬photosynthesis )H20 + CO2) ‫الضوئ‬ ‫ي‬ ‫البناء‬ All animals are reliant on carbohydrate as a source of energy ‫مصدر للطاقة‬ Carbohydrates are found in: MCQ ‫الحتة دي مهمة‬ a) Plants in the form of starch and cellulose b) Animals in the form of glycogen in liver ‫ الكبد‬and muscle ‫العضالت‬ Sources of Carbohydrates Bread Beans Potatoes Milk soft drinks corn Smart Not Hard 1 Bio-Philic Dr. Ibrahim El-Husseiny Classification Of Carbohydrates 1 Monosacchaarides contain single sugar unit 2 Disaccharides contain 2 sugar units 3 Oligosaccharides contain 3 to 10 sugar units 4 Polysaccharides contain more than 10 units Monosaccharides They are the simplest sugars ‫اﺑﺴﻂ اﻧﻮاع اﻟﺴﻜﺮ‬ They are the building units of carbohydrates ‫اﻟﻮﺣﺪة اﻟﺒﻨﺎﺋﯿﺔ‬ Their general formula is CnH2nOn MCQ ‫اﻟﺣﺗﺔ دي ﻣﮭﻣﺔ‬ Classification of Monosaccharides A. According to active group: 1) Aldoses : contain aldehyde group 2) Ketoses : contain ketone group Smart Not Hard 2 Bio-Philic Dr. Ibrahim El-Husseiny B. According to the number of carbon atoms:  3 Carbons: triose  4 Carbons: tetrose  5 Carbons: pentose  6 Carbons: hexose  7 Carbons: heptose C. According to number of carbon atom and active group: 4 ‫ و‬5 ‫ﺻﻔﺣﺔ‬ Studying medicine without teacher is like a sailing without boat, and studying biochemistry without Ibrahim El-Husseiny is like not going to the sea at all ! Smart Not Hard 3 Bio-Philic Dr. Ibrahim El-Husseiny ‫اﻟﺼﻴﻎ اﻟﻜﻴﻤﻴﺎﺋﻴﺔ ﻟﻠﻔﻬﻢ ﻓﻘﻂ‬ Aldoses Ketoses Trios Glyceraldehyde Dihydroxyacetone aldehyde ‫ ذرات كربون والمجموعة الفعالة‬3 ‫يحتوي علي‬ ketone ‫ ذرات كربون والمجموعة الفعالة‬3 ‫يحتوي علي‬ Tetrose Erythrose Erythroulose aldehyde ‫ ذرات كربون والمجموعة الفعالة‬4 ‫يحتوي علي‬ ketone ‫ ذرات كربون والمجموعة الفعالة‬4 ‫يحتوي علي‬ Pentose Ribose Xylose Ribulose Xyloulose Smart Not Hard 4 Bio-Philic Dr. Ibrahim El-Husseiny Aldoses Ketoses Hexoses Mannose Glucose Galactose Fructose Heptoses Heptose Sedoheptulose Smart Not Hard 5 Bio-Philic Dr. Ibrahim El-Husseiny ‫ ُﻣ ِﮭ ﱠﻣﺔٌ ِﺟدا‬MCQ 1) Hexoses are the most common forms of monosaccharides 2) Trioses are the smallest form of monosaccharides 3) The active group is called anomeric carbon (C1 in aldoses or C2 in ketoses) Now, Show me your intelligence; the smallest monosacchride is: a) Sedoheptulose b) Galactose c) Glyceraldehyde d) Ribose Biological importance of monosaccharides 1) Ribose RNA 2) Deoxyribose DNA 3) Glucose: is the sugar of blood ‫اﻟﺪم‬ 4) Fructose: is the sugar of the semen ‫اﻟﺴﺎﺋﻞ اﻟﻤﻨﻮي‬ 5) Galactose: formed in mammary gland ‫اﻟﻐﺪد اﻟﺜﺪﯾﯿﺔ‬ to make lactose (milk sugar) 6) Mannose: enter the structure of glycoproteins ‫ﺑﺮوﺗﯿﻦ ﺳﻜﺮي‬ 7) Inositol (sugar alcohol)  muscle sugar Smart Not Hard 6 Bio-Philic Dr. Ibrahim El-Husseiny Physical Properities Of Monosaccharides 1) Asymmetrical carbon atom (chiral carbon) It is the carbon atom that attatched to four different chemical groups All momosaccharides contain assymetrical carbon atom except dihydroxyacetone 2) isomers (‫)اﻟﻨﻈﺎﺋﺮ‬  Def: compounds with the same chemical groups but differ in arrangment of these groups (due to prscence of asymmetrical carbon atom)  Types: a) D & L isomers (configuration) There are 2 forms of monosaccharides according to the attachment of OH group of the subterminal carbon ‫الكربونة قبل االخيرة‬ a) If the OH is attatched to the right side → the sugar is called D b) If the OH is attatched to the left side → the sugar is called L The difference make the 2 forms (D & L) mirror image to each other. Almost all naturally occurring carbohydrates are of D configuration Smart Not Hard 7 Bio-Philic Dr. Ibrahim El-Husseiny b) Functional group isomers These isomers have the same carbon skeleton and the same position of groups but differ in functional active groups (aldehyde or ketone) e.g: glucose and fructose c) Epimers They are isomers which differ in distribution of OH groups around a single assymmetric carbon atom other than the anomeric and the subterminal Glucose is an epimer to mannose at C 2 Glucose is an epimer to galactose at C 4 But mannose and galactose are not epimers. Mannose Glucose Galactose d) Anomers They are isomers different in distribution of OH group around the asymmetric anomeric carbon atom ( C1 in aldoses & C2 In ketoses ) in ring form e.g: α glucose and β glucose N.B. α and β are convertible to each other (mutarotation) N.B. equilibrium of solution occurs when it contains 66% β and 33% α and 1 % in open chain Smart Not Hard 8 Bio-Philic Dr. Ibrahim El-Husseiny Glycosides  Definition:  Compounds result from condenstation between monosaccharide and another compound  The another compound may be: a) Monosaccharide b) Aglycon (non carbohydrate compound)  Examples of glycosides Disaccharides (‫ ﺳﻜﺮ‬+ ‫)سكر‬ Sugar Nucleotides )‫ فوسفات‬+ ‫ ﺳﻜﺮ‬+ ‫(قاعدة نيتروجينية‬ Glycolipid )‫ ﺳﻜﺮ‬+ ‫(دهون‬ Glycoproteins )‫ ﺳﻜﺮ‬+ ‫(بروتين‬ Digitalis (Cardiac glycosides) )‫ ﺳﻜﺮ‬+ ‫(ستيرويد‬ Some Antibiotics as Streptomycin (‫ ﺳﻜﺮ‬+ NH2) Digitalis The aglycon part is steroid Digitalis is used for treatment of heart failure (because it inhibits the enzyme Na , K pump of cell membrane) Smart Not Hard 9 Bio-Philic Dr. Ibrahim El-Husseiny Monosaccharide derivatives 1) Deoxy sugar  These are sugars in which OH group of C2 is replaced by hydrogen.  Example: Ribose is converted into deoxyribose Ribose Deoxy-Ribose 2) Amino Sugars They are produced by replacing OH group on C2 by an amino group (NH2). Example : glucosamine & mannosamine Importance of amino sugars a) Formation of glycoprotein, proteoglycan and gangliosides. b) Some antibiotics contain amino sugar such as erthromycin. mannosamine Smart Not Hard 10 Bio-Philic Dr. Ibrahim El-Husseiny 3) Amino sugar acids Pyruvic  These are formed by addition of acids to amino sugars. acid a) Neuraminic acid: mannosamine and pyruvic acid b) sialic acid: N Acetyl Neuraminic Acid (NANA). Importance of NANA: Acetyl a) This negatively charged residue is found in glycoproteins present in cell membrane. b) Enters in compositions of gangliosides. c) Important in the biology of pathogenic bacteria. 4) sugar alcohols  Reduction of monosaccharides gives sugar alcohols. Ribose reduction gives Ribitol that is a part of the structure of vitamin B2 (Riboflavin). Glucose Reduction gives sorbitol or glucitol that enters in medical industries. Fructose reduction gives Sorbitol or Mannitol. Inositol: It is a hexahydric alcohol (6 OH groups).It presents in high concentration in heart and muscles tissues, so it is called muscle sugar. Smart Not Hard 11 Bio-Philic Dr. Ibrahim El-Husseiny 5) Sugar acids  Aldoses may be oxidized to 3 types of acids: a- Aldonic acids:  aldehyde group is oxidised to a carboxyl group.  D- Glucose is converted to gluconic acid  L-glucose is converted to L-ascorbic acid ( vitamin C) b- Uronic acids:  primary alcohol (CH2OH) (last carbon) is oxidized to COOH.  D- Glucose is converted to D-glucuronic acid Smart Not Hard 12 Bio-Philic Dr. Ibrahim El-Husseiny Importance of glucuronic acid: 1-Glucuronic acid is often linked to xenobiotic substances such as drugs, pollutants. 2- Conjugation with bilirubin, and steroid hormones. 3-Formation of glycosaminoglycans. c- Saccharicacids :  oxidation at both ends of monosaccharide.  Glucose is converted to glucaric (saccharic acid). Smart Not Hard 13 Bio-Philic Dr. Ibrahim El-Husseiny Disaccharides Formed by condensation between 2 monosaccharides. The bond between them is called glycosidic bond. 1) Maltose  Maltose is called malt or corn sugar  Structure: 2 α-glucose linked by α-1,4 glycosidic bond α-glucose α-glucose Maltose Smart Not Hard 14 Bio-Philic Dr. Ibrahim El-Husseiny 2) lactose  Lactose is called milk sugar (it make up around 4.5 – 5 % of milk)  Lactose is non fermentable.  Structure: β-galactose + β-glucose linked by β-1,4 glycosidic bond β-galactose β-glucose Lactose Smart Not Hard 15 Bio-Philic Dr. Ibrahim El-Husseiny 3) Sucrose  Sucrose is called table sugar or sugar beets oe sugar cane  Structure: α-glucose + β-fructose linked by α-1 and β-2 glycosidic bond Sucrose 4) lactulose Structure: β-galactose and β- fructose linked by β 1,4 glycosidic bond. Smart Not Hard 16 Bio-Philic Dr. Ibrahim El-Husseiny Clinical importance of Lactulose:  lactulose is is non-absorbable so used in treatment of constipation & hepatic encephalopathy  The osmotic activity of lactulose will cause diarrhea → which will move toxic products  in colon; bacterial flora convert lactulose into organic acid  organic acid help NH3 to converted into NH4 (ammonium)  NH4 can’t diffuse into blood → trapping of ammonia in colon. Polysaccharides  Def: compounds formed of more than 10 monosaccharide units linked by glycosidic bonds.  Types: Homopolysaccharides Heteropolysaccharides Smart Not Hard 17 Bio-Philic Dr. Ibrahim El-Husseiny Homopolysaccharides Composed of repeated units of similar monosacchrides. 1- Glycogen 2- Starch 3- Cellulose Site Liver & muscle Cereals, potatoes & vegetables Wall of Plant cell The storage form of Prevent The storage form of carbohydrates in Function carbohydrates in plants constipation animals Highly branched Amylopectins Amylose Outer part (80%) Inner part (20%) molecule consists of α- glucose units linked by Each chain composed of Contains only β- gluose units α-1,4 glycosidic bonds 20-30 glucose units α 1,4 linked by β 1,4 Structure at straight chains linked by α 1,4 glycosidic glycosidic bonds and α 1,6 glycosidic glycosidic bonds at bonds with no branches bonds at branched straight chains and with no points. α 1,6 glycosidic bonds branches at branched points. Functions of cellulose:  Cellulose not digested by human bodies due to absence of hydrolytic enzymes that attack β-link. So it prevents constipation as it forms the main bulk of stool (but digested by cows (ruminanats) N.B. 1) Maltose results from Partial hydrolysis of starch by amylase enzyme in saliva. 2) Glucose results from complete hydrolysis of starch Smart Not Hard 18 Bio-Philic Dr. Ibrahim El-Husseiny Smart Not Hard 19  Bio-Philic Dr. Ibrahim El-Husseiny Heteropolysaccharides: Glycos-amino-glycans (GAGs)  Properties 1) They are present extracellular except heparin. 2) They are structural component of connective tisuue. 3) Formed of repeated disaccharide units (uronic acid + an amino sugar) Types Keratan chondroitin Dermatan Hyaluronic acid: Heparin sulfate sulfate: sulfate: β-glucouronic acid + β-N-acetyl sulfated iduronic acid at C2 Structure glucosamine. + sulfated glucosamine at Hyaluronic acid is sulfate free C2, C6 Cartlige → Synovial fluid -Vitreous humor of giving it much Site the eye - Embryonic tissue – Mast cells Cartlige resistance for skin Cartilage- Skin - Umbilical cord compression. 1) Gel made of hyaluronic acid has 1) Prevent blood clotting Large and With good resistance to compression (anticoagulant) highly glucosamine → 2) Combats (prevent) osteoarthritis hydrated used in Function 3) Lubricant and shock absorber. 2) Stimulates lipoprotein molecule, treatment of and clinical 4) Skin moisture lipase enzyme that which acts as a osteoarthritis importance 5) Part of cementing ground hydrolyze lipids. cushion in substance. joints 6) Aids in wound healing Smart Not Hard 20 Bio-Philic Dr. Ibrahim El-Husseiny Notes Hyaluronidase enzyme  Definition: the enzyme that hydrolyze hyaluronic acid.  Site: a) It is secreted by invasive bacteria. It helps the spread of bacteria through subcutaneous tissue. b) It is also present in sperm and helps fertilization.  Clinical importance of hyaluronidase enzyme:  Hyaluronidase has been used to enhance (increase) the absorption of fluids given by subcutaneous injection or intramuscular injection , and to improve the diffusion of local anesthetics.  Drugs whose subcutaneous administration has been facilitated in this way include morphine , insulin , and immunoglobulins. Clinical uses of heparin:  Heparin is used as anti-thrombotic to treat and prevent thromboembolic events,  as well as for systemic anti-coagulation during cardiopulmonary bypass and dialysis. Smart Not Hard 21  Bio-Philic Dr. Ibrahim El-Husseiny Proteoglycans and glycoproteins (Conjugate) Both are proteins containing carbohydrates ,but: 1) They contain different Sugars. 2) They have different Structures. 3) They are present in different Sites. 4) They perform different functions. Proteoglycans  Definition: Proteins are combined with carbohydrates called glycosaminoglycans (mucopoly-saccharide)  Structure: they are composed of protein core attached to unbranched chain of glycosaminoglycans. Glycoproteins (Mucoproteins)  Definition carbohydrates attached to protein core  These carbohydrates may be: a) Pentoses: arabinose, xylose. b) Hexoses: galactose, mannose. c) Sialic acid. d) N acetyl glucosamines, N acetyl galactosamines.  But it does not contain glucose – glucuronic acid – sulfate group  Functions of glycoproteins 1) Cell surface Receptors. 2) Some Enzymes are glycoproteins 3) Some Hormones as lutenizing hormone (LH) are glycoproteins 4) Act as Lubricants in mucin of GIT, respiratoty and urogenital tracts. 5) Antibodies (Immunoglobulins) , interferon, complement factors are glycoproteins. Smart Not Hard 22 Bio-Philic Dr. Ibrahim El-Husseiny 6) Recognition signals: blood groups are a good example:  There are four major blood groups in humans: A, B, AB, and O  Structure of blood group antigen: 1) Glycophorin A (Integral protein present on cell membrane of RBCs) 2) Oligosaccharide attatched to glycophorin A 3) The oligosaccharide can have a different Terminal sugars or not.  This terminal sugar determine the type of blood group  This terminal sugar is added by different types of glycosyl transferases enzyme  as in blood group A, B & AB  Some individuals do not have glycosyl transferases enzyme to add the terminal sugar  as in blood group O Smart Not Hard 23 Bio-Philic Dr. Ibrahim El-Husseiny Importance of carbohydrates 1. The major Source of energy in both animal & plants 2. Carbohydrates are used in Synthesis of cell surface receptors (short chains linked to lipids and proteins) 3. Carbohydrates are used to form Structural elements ,such as chitin in animals and cellulose in plants 4. Carbohydrates considered as building blocks ‫ وحدات بنائية‬for other molecules: (e.g. conversion to fat, amino acids, nucleic acids) 5. Carbohydrates in the form of fibers can help to lower blood glucose and cholesterol levels and prevent constipation Smart Not Hard 24